Many thanks for the replies about the lack of vacuum on my '61 LeBaron Clearly there was no way I could increase the cranking vacuum, so I have found a vacuum pump off a scrap Jaguar (C. body Caddies are are a little thin on the ground in the U.K.), and rigged it with the help of a relay to close the air restrictor while the starter is running and LPG is selected. As soon as the starter is released, the pump cuts out and the engine takes over. The result, easy, automatic start-up on LPG every time. Now I can get best performance on both LPG and Gasoline. All the best, Tony V.